DNS Records Defined

Every domain has a specific IP address it corresponds to. This IP address indicates the “home” or server where the content being requested is located. DNS is essentially a map of records pointing specific aspects of your domain (www, ftp, mail, etc) to their home. This article will explain individual DNS records; what they mean and how they are used.

An Example DNS Zone viewed through the Portal

A Record

The DNS "A Record" short for Address Record is used to map hostnames to an IP address. All DNS A Records must resolve to an IP address. In the example above you will see the A record for hdctest.com resolves to 1.2.3.4 therefore any requests to http://hdctest.com would be directed to the server IP 1.2.3.4. You will also see for this particular zone there is an A record of mail which also resolves to 1.2.3.4 therefore any requests to http://mail.hdctest.com would be directed to the server IP 1.2.3.4.

CNAME Record

The DNS "CNAME Record" short for Canonical Name Record is an alias or nickname for a record in a DNS Zone. All DNS CNAME Records must resolve to a fully qualified domain name. In the example above you will see CNAME records for www and ftp which resolve to hdctest.com. When a request is made for http://www.hdctest.com or http://ftp.hdctest.com the server will look at the primary A record for hdctest.com and resolve traffic to 1.2.3.4.

Another way of looking at this is you could have a CNAME of google with a value of google.com therefore any requests to http://google.hdctest.com would load Google.com.

MX Record

The DNS "MX Record" short for Mail Exchange Record specifies a mail server responsible for accepting email messages on behalf of the specified domain. All DNS MX Records must resolve to a fully qualified domain name. In the example above you will see the MX record for hdctest.com is mail.hdctest.com therefore all email requests for hdctest.com will be handled by mail.hdctest.com which resolves to 1.2.3.4.

A DNS Zone may contain several MX records which offers redundancy in the event that the mail server is unavailable. In the example above we only have one MX record however you will note the (10) next to MX in the Type column; this is the record priority. The smallest preference number has the highest priority and any server with the smallest preference number must be tried first. Therefore if a secondary record of MX(20) exists mail delivery will first be attempted to the MX(10) record and if the server is non-responsive mail delivery will be attempted to the secondary record MX(20).

TXT Record

The DNS "TXT Record" short for Text Record is used to specify text strings such as SPF Records, DomainKeys, etc. In the example above you will see a TXT record of "v=spf1 include:spf.safesecureweb.com ~all" which is a valid SPF record. For more information on generating SPF Records please see http://old.openspf.org/wizard.html